Methods and apparatus for beamforming and initial access

ABSTRACT

A method and apparatus for determining Physical Random Access Channel (PRACH) resources and using beams are disclosed herein. In an example, a wireless transmit/receive unit (WTRU) may measure a plurality of beam reference signals transmitted from a base station. Further, the WTRU may select a beam reference signal from among the plurality of measured beam reference signals. Also, the WTRU may receive a configuration message from the base station that includes correspondence information regarding the plurality of beam reference signals, wherein the correspondence information designates at least one set of PRACH resources for each of the plurality of beam reference signals. In addition, the WTRU may determine a set of PRACH resources designated for the selected beam reference signal based on the received correspondence information. Moreover, the WTRU may transmit a PRACH signal using at least one PRACH resource of the determined set of PRACH resources.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/669,291 filed Aug. 4, 2017, which a continuation of U.S. patentapplication Ser. No. 14/763,113 filed Jul. 23, 2015, which is the U.S.National Stage, under 35 U.S.C. § 371, of International Application No.PCT/US2014/012914 filed Jan. 24, 2014, which claims the benefit of U.S.Provisional Patent Application No. 61/756,792 filed Jan. 25, 2013, thecontents of which are hereby incorporated by reference herein.

BACKGROUND

A reference signal (RS) may be classified as a wireless transmit/receiveunit (WTRU)-specific reference (WTRU-RS) and a cell-specific referencesignaling (CRS). The WTRU-RS may be used on for a specific WTRU so thatthe RS is transmitted for the resources allocated to the WTRU. On theother hand, the CRS may be shared by all WTRUs in a cell so that the RSis transmitted in a wideband manner. In addition, according to the usageof the RS, it may be further differentiated to at least one of ademodulation reference signal (DM-RS) and a channel-state-informationreference signal (CSI-RS).

The DM-RS may be used only for a specific WTRU and the RS is typicallyprecoded to exploit beamforming gain. The CRS may be defined for allWTRUs in a cell and may be used for demodulation and measurementpurposes.

SUMMARY

A method and apparatus for determining a beam for reception aredisclosed herein. A method in a wireless transmit/receive unit (WTRU)includes that the WTRU may receive a broadcast message from an evolvedNode B (eNB) that includes information associated with a plurality ofbeam reference signals, wherein the information includes at least oneset of Physical Random Access Channel (PRACH) resources associated witheach of the plurality of beam reference signals. Further, the WTRU maymeasure reference signals transmitted on each of the plurality of beamreference signals. Then, the WTRU may select a beam reference signalfrom among the plurality of beam reference signals. In addition, theWTRU may transmit a PRACH preamble in a set of resources associated withthe selected beam reference signal. The WTRU may then receive furthercommunications from the eNB.

In an example, the information associated with the plurality of beamreference signals may include a plurality of measurement configurations.In another example, the PRACH preamble may be transmitted on anallocated frequency associated with the set of resources.

In a further example, the WTRU may select a beam reference signal basedon a determination that a measured reference signal power is better onat least one beam reference signal. Also, the WTRU may select a beamreference signal based on predetermined criteria.

In an additional example, at least one set of PRACH resources may beportioned based on the number of the plurality of beam referencesignals. In yet a further example, the beam reference signals may bebeam tracking reference signals. Also, the beam reference signals may beChannel State Information-Reference Signals (CSI-RSs). In still afurther example, the beam may be a 3-D beam.

In an additional example, an eNB may perform a method for determining avertical beam for transmission. For example, the eNB may transmit abroadcast message to a WTRU that includes two or more CSI-RSconfigurations. Further, the eNB may receive a first measurement reportfrom the WTRU including a received signal-to-interference plus noiseratio (SINR) metric for a cell-specific CSI-RS in an uplink subframe.Also, the eNB may receive a second measurement report from the WTRUincluding an SINR metric for each antenna port in the cell-specificCSI-RS associated with a vertical beam. In a further example, thetransmitting communications may be based on the first measurement reportand the second measurement report.

Another method and apparatus for determining a vertical beam forreception are disclosed herein. A method in a WTRU includes receiving abroadcast message from an eNB that includes information associated witha plurality of vertical beams, wherein the information includes at leastone set of PRACH resources associated with each of the plurality ofvertical beams, measuring reference signals transmitted on each of theplurality of vertical beams to select a reception vertical beam,transmitting a PRACH preamble in a set of resources associated with theselected reception vertical beam, and receiving communications from theeNB using the selected reception vertical beam.

A method and apparatus for determining PRACH resources and using beamsare disclosed herein. In an example, a WTRU may measure a plurality ofbeam reference signals transmitted from a base station. Further, theWTRU may select a beam reference signal from among the plurality ofmeasured beam reference signals. Also, the WTRU may receive aconfiguration message from the base station that includes correspondenceinformation regarding the plurality of beam reference signals, whereinthe correspondence information designates at least one set of PRACHresources for each of the plurality of beam reference signals. In anexample, the configuration message may be a broadcast message. Inanother example, the configuration message may be a radio resourcecontrol (RRC) message. In addition, the WTRU may determine a set ofPRACH resources designated for the selected beam reference signal basedon the received correspondence information. Moreover, the WTRU maytransmit a PRACH signal using at least one PRACH resource of thedetermined set of PRACH resources. The WTRU may then receive furthercommunications from the eNB.

In a further example, the correspondence information regarding theplurality of beam reference signals may include a plurality ofmeasurement configurations. In yet another example, the determined setof PRACH resources may include at least one PRACH preamble. Further, thePRACH signal may be a PRACH preamble in the determined set of PRACHresources. In still another example, the WTRU may select a beamreference signal based on a determination that a measured beam referencesignal power is better than a threshold on at least one beam referencesignal.

In an additional example, the determined set of PRACH resources mayinclude at least one set of time resources. Further, the PRACH signalmay be transmitted in one of the time resources of the set of timeresources. Also, the PRACH signal may be based on the receivedcorrespondence information.

BRIEF DESCRIPTION OF THE DRAWINGS

A more detailed understanding may be had from the following description,given by way of example in conjunction with the accompanying drawings,wherein:

FIG. 1A is a system diagram of an example communications system in whichone or more disclosed embodiments may be implemented;

FIG. 1B is a system diagram of an example wireless transmit/receive unit(WTRU) that may be used within the communications system illustrated inFIG. 1A;

FIG. 1C is a system diagram of an example radio access network and anexample core network that may be used within the communications systemillustrated in FIG. 1A;

FIG. 2 is a diagram of a WTRU-specific precoded demodulation referencesignal (DM-RS);

FIG. 3 is a diagram of a non-precoded cell-specific reference signal(RS);

FIG. 4 is a diagram of a WTRU-specific DM-RS for a normal cyclic prefix(CP);

FIG. 5 is a diagram of a cell-specific reference signal (CRS) structureaccording to the number of antenna ports;

FIG. 6 is a diagram of a DM-RS pattern supporting up to eight layers;

FIG. 7 is a diagram of a channel state information reference signal(CSI-RS) patterns reuse according to the number of ports;

FIG. 8 is a timing diagram of an example of periodic reporting;

FIG. 9 is a block diagram of a an active antenna system (AAS) radioarchitecture;

FIG. 10 is a diagram of vertical sectorization with the AAS radioarchitecture;

FIG. 11 is a diagram of WTRU-specific elevation beamforming using AAS;

FIG. 12 is a diagram of a contention-based random access procedure;

FIG. 13 is a diagram of a downlink beam tracking reference signal(d-BTRS) using a four port CSI-RS pattern; and

FIG. 14 is an example method for receiving a reception vertical beam.

DETAILED DESCRIPTION

FIG. 1A is a diagram of an example communications system 100 in whichone or more disclosed embodiments may be implemented. The communicationssystem 100 may be a multiple access system that provides content, suchas voice, data, video, messaging, broadcast, etc., to multiple wirelessusers. The communications system 100 may enable multiple wireless usersto access such content through the sharing of system resources,including wireless bandwidth. For example, the communications systems100 may employ one or more channel access methods, such as code divisionmultiple access (CDMA), time division multiple access (TDMA), frequencydivision multiple access (FDMA), orthogonal FDMA (OFDMA), single-carrierFDMA (SC-FDMA), and the like.

As shown in FIG. 1A, the communications system 100 may include wirelesstransmit/receive units (WTRUs) 102 a, 102 b, 102 c, 102 d, a radioaccess network (RAN) 104, a core network 106, a public switchedtelephone network (PSTN) 108, the Internet 110, and other networks 112,though it will be appreciated that the disclosed embodiments contemplateany number of WTRUs, base stations, networks, and/or network elements.Each of the WTRUs 102 a, 102 b, 102 c, 102 d may be any type of deviceconfigured to operate and/or communicate in a wireless environment. Byway of example, the WTRUs 102 a, 102 b, 102 c, 102 d may be configuredto transmit and/or receive wireless signals and may include userequipment (UE), a mobile station, a fixed or mobile subscriber unit, apager, a cellular telephone, a personal digital assistant (PDA), asmartphone, a laptop, a netbook, a personal computer, a wireless sensor,consumer electronics, and the like.

The communications systems 100 may also include a base station 114 a anda base station 114 b. Each of the base stations 114 a, 114 b may be anytype of device configured to wirelessly interface with at least one ofthe WTRUs 102 a, 102 b, 102 c, 102 d to facilitate access to one or morecommunication networks, such as the core network 106, the Internet 110,and/or the networks 112. By way of example, the base stations 114 a, 114b may be a base transceiver station (BTS), a Node-B, an eNode B, a HomeNode B, a Home eNode B, a site controller, an access point (AP), awireless router, and the like. While the base stations 114 a, 114 b areeach depicted as a single element, it will be appreciated that the basestations 114 a, 114 b may include any number of interconnected basestations and/or network elements.

The base station 114 a may be part of the RAN 104, which may alsoinclude other base stations and/or network elements (not shown), such asa base station controller (BSC), a radio network controller (RNC), relaynodes, etc. The base station 114 a and/or the base station 114 b may beconfigured to transmit and/or receive wireless signals within aparticular geographic region, which may be referred to as a cell (notshown). The cell may further be divided into cell sectors. For example,the cell associated with the base station 114 a may be divided intothree sectors. Thus, in one embodiment, the base station 114 a mayinclude three transceivers, i.e., one for each sector of the cell. Inanother embodiment, the base station 114 a may employ multiple-inputmultiple output (MIMO) technology and, therefore, may utilize multipletransceivers for each sector of the cell.

The base stations 114 a, 114 b may communicate with one or more of theWTRUs 102 a, 102 b, 102 c, 102 d over an air interface 116, which may beany suitable wireless communication link (e.g., radio frequency (RF),microwave, infrared (IR), ultraviolet (UV), visible light, etc.). Theair interface 116 may be established using any suitable radio accesstechnology (RAT).

More specifically, as noted above, the communications system 100 may bea multiple access system and may employ one or more channel accessschemes, such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA, and the like. Forexample, the base station 114 a in the RAN 104 and the WTRUs 102 a, 102b, 102 c may implement a radio technology such as Universal MobileTelecommunications System (UMTS) Terrestrial Radio Access (UTRA), whichmay establish the air interface 116 using wideband CDMA (WCDMA). WCDMAmay include communication protocols such as High-Speed Packet Access(HSPA) and/or Evolved HSPA (HSPA+). HSPA may include High-Speed DownlinkPacket Access (HSDPA) and/or High-Speed Uplink Packet Access (HSUPA).

In another embodiment, the base station 114 a and the WTRUs 102 a, 102b, 102 c may implement a radio technology such as Evolved UMTSTerrestrial Radio Access (E-UTRA), which may establish the air interface116 using Long Term Evolution (LTE) and/or LTE-Advanced (LTE-A).

In other embodiments, the base station 114 a and the WTRUs 102 a, 102 b,102 c may implement radio technologies such as IEEE 802.16 (i.e.,Worldwide Interoperability for Microwave Access (WiMAX)), CDMA2000,CDMA2000 1X, CDMA2000 EV-DO, Interim Standard 2000 (IS-2000), InterimStandard 95 (IS-95), Interim Standard 856 (IS-856), Global System forMobile communications (GSM), Enhanced Data rates for GSM Evolution(EDGE), GSM EDGE (GERAN), and the like.

The base station 114 b in FIG. 1A may be a wireless router, Home Node B,Home eNode B, or access point, for example, and may utilize any suitableRAT for facilitating wireless connectivity in a localized area, such asa place of business, a home, a vehicle, a campus, and the like. In oneembodiment, the base station 114 b and the WTRUs 102 c, 102 d mayimplement a radio technology such as IEEE 802.11 to establish a wirelesslocal area network (WLAN). In another embodiment, the base station 114 band the WTRUs 102 c, 102 d may implement a radio technology such as IEEE802.15 to establish a wireless personal area network (WPAN). In yetanother embodiment, the base station 114 b and the WTRUs 102 c, 102 dmay utilize a cellular-based RAT (e.g., WCDMA, CDMA2000, GSM, LTE,LTE-A, etc.) to establish a picocell or femtocell. As shown in FIG. 1A,the base station 114 b may have a direct connection to the Internet 110.Thus, the base station 114 b may not be required to access the Internet110 via the core network 106.

The RAN 104 may be in communication with the core network 106, which maybe any type of network configured to provide voice, data, applications,and/or voice over internet protocol (VoIP) services to one or more ofthe WTRUs 102 a, 102 b, 102 c, 102 d. For example, the core network 106may provide call control, billing services, mobile location-basedservices, pre-paid calling, Internet connectivity, video distribution,etc., and/or perform high-level security functions, such as userauthentication. Although not shown in FIG. 1A, it will be appreciatedthat the RAN 104 and/or the core network 106 may be in direct orindirect communication with other RANs that employ the same RAT as theRAN 104 or a different RAT. For example, in addition to being connectedto the RAN 104, which may be utilizing an E-UTRA radio technology, thecore network 106 may also be in communication with another RAN (notshown) employing a GSM radio technology.

The core network 106 may also serve as a gateway for the WTRUs 102 a,102 b, 102 c, 102 d to access the PSTN 108, the Internet 110, and/orother networks 112. The PSTN 108 may include circuit-switched telephonenetworks that provide plain old telephone service (POTS). The Internet110 may include a global system of interconnected computer networks anddevices that use common communication protocols, such as thetransmission control protocol (TCP), user datagram protocol (UDP) andthe internet protocol (IP) in the TCP/IP internet protocol suite. Thenetworks 112 may include wired or wireless communications networks ownedand/or operated by other service providers. For example, the networks112 may include another core network connected to one or more RANs,which may employ the same RAT as the RAN 104 or a different RAT.

Some or all of the WTRUs 102 a, 102 b, 102 c, 102 d in thecommunications system 100 may include multi-mode capabilities, i.e., theWTRUs 102 a, 102 b, 102 c, 102 d may include multiple transceivers forcommunicating with different wireless networks over different wirelesslinks. For example, the WTRU 102 c shown in FIG. 1A may be configured tocommunicate with the base station 114 a, which may employ acellular-based radio technology, and with the base station 114 b, whichmay employ an IEEE 802 radio technology.

FIG. 1B is a system diagram of an example WTRU 102. As shown in FIG. 1B,the WTRU 102 may include a processor 118, a transceiver 120, atransmit/receive element 122, a speaker/microphone 124, a keypad 126, adisplay/touchpad 128, non-removable memory 106, removable memory 132, apower source 134, a global positioning system (GPS) chipset 136, andother peripherals 138. It will be appreciated that the WTRU 102 mayinclude any sub-combination of the foregoing elements while remainingconsistent with an embodiment.

The processor 118 may be a general purpose processor, a special purposeprocessor, a conventional processor, a digital signal processor (DSP), aplurality of microprocessors, one or more microprocessors in associationwith a DSP core, a controller, a microcontroller, Application SpecificIntegrated Circuits (ASICs), Field Programmable Gate Array (FPGAs)circuits, any other type of integrated circuit (IC), a state machine,and the like. The processor 118 may perform signal coding, dataprocessing, power control, input/output processing, and/or any otherfunctionality that enables the WTRU 102 to operate in a wirelessenvironment. The processor 118 may be coupled to the transceiver 120,which may be coupled to the transmit/receive element 122. While FIG. 1Bdepicts the processor 118 and the transceiver 120 as separatecomponents, it will be appreciated that the processor 118 and thetransceiver 120 may be integrated together in an electronic package orchip.

The transmit/receive element 122 may be configured to transmit signalsto, or receive signals from, a base station (e.g., the base station 114a) over the air interface 116. For example, in one embodiment, thetransmit/receive element 122 may be an antenna configured to transmitand/or receive RF signals. In another embodiment, the transmit/receiveelement 122 may be an emitter/detector configured to transmit and/orreceive IR, UV, or visible light signals, for example. In yet anotherembodiment, the transmit/receive element 122 may be configured totransmit and receive both RF and light signals. It will be appreciatedthat the transmit/receive element 122 may be configured to transmitand/or receive any combination of wireless signals.

In addition, although the transmit/receive element 122 is depicted inFIG. 1B as a single element, the WTRU 102 may include any number oftransmit/receive elements 122. More specifically, the WTRU 102 mayemploy MIMO technology. Thus, in one embodiment, the WTRU 102 mayinclude two or more transmit/receive elements 122 (e.g., multipleantennas) for transmitting and receiving wireless signals over the airinterface 116.

The transceiver 120 may be configured to modulate the signals that areto be transmitted by the transmit/receive element 122 and to demodulatethe signals that are received by the transmit/receive element 122. Asnoted above, the WTRU 102 may have multi-mode capabilities. Thus, thetransceiver 120 may include multiple transceivers for enabling the WTRU102 to communicate via multiple RATs, such as UTRA and IEEE 802.11, forexample.

The processor 118 of the WTRU 102 may be coupled to, and may receiveuser input data from, the speaker/microphone 124, the keypad 126, and/orthe display/touchpad 128 (e.g., a liquid crystal display (LCD) displayunit or organic light-emitting diode (OLED) display unit). The processor118 may also output user data to the speaker/microphone 124, the keypad126, and/or the display/touchpad 128. In addition, the processor 118 mayaccess information from, and store data in, any type of suitable memory,such as the non-removable memory 106 and/or the removable memory 132.The non-removable memory 106 may include random-access memory (RAM),read-only memory (ROM), a hard disk, or any other type of memory storagedevice. The removable memory 132 may include a subscriber identitymodule (SIM) card, a memory stick, a secure digital (SD) memory card,and the like. In other embodiments, the processor 118 may accessinformation from, and store data in, memory that is not physicallylocated on the WTRU 102, such as on a server or a home computer (notshown).

The processor 118 may receive power from the power source 134, and maybe configured to distribute and/or control the power to the othercomponents in the WTRU 102. The power source 134 may be any suitabledevice for powering the WTRU 102. For example, the power source 134 mayinclude one or more dry cell batteries (e.g., nickel-cadmium (NiCd),nickel-zinc (NiZn), nickel metal hydride (NiMH), lithium-ion (Li-ion),etc.), solar cells, fuel cells, and the like.

The processor 118 may also be coupled to the GPS chipset 136, which maybe configured to provide location information (e.g., longitude andlatitude) regarding the current location of the WTRU 102. In additionto, or in lieu of, the information from the GPS chipset 136, the WTRU102 may receive location information over the air interface 116 from abase station (e.g., base stations 114 a, 114 b) and/or determine itslocation based on the timing of the signals being received from two ormore nearby base stations. It will be appreciated that the WTRU 102 mayacquire location information by way of any suitablelocation-determination method while remaining consistent with anembodiment.

The processor 118 may further be coupled to other peripherals 138, whichmay include one or more software and/or hardware modules that provideadditional features, functionality and/or wired or wirelessconnectivity. For example, the peripherals 138 may include anaccelerometer, an e-compass, a satellite transceiver, a digital camera(for photographs or video), a universal serial bus (USB) port, avibration device, a television transceiver, a hands free headset, aBluetooth® module, a frequency modulated (FM) radio unit, a digitalmusic player, a media player, a video game player module, an Internetbrowser, and the like.

FIG. 1C is a system diagram of the RAN 104 and the core network 106according to an embodiment. As noted above, the RAN 104 may employ anE-UTRA radio technology to communicate with the WTRUs 102 a, 102 b, 102c over the air interface 116. The RAN 104 may also be in communicationwith the core network 106.

The RAN 104 may include eNode-Bs 140 a, 140 b, 140 c, though it will beappreciated that the RAN 104 may include any number of eNode-Bs whileremaining consistent with an embodiment. The eNode-Bs 140 a, 140 b, 140c may each include one or more transceivers for communicating with theWTRUs 102 a, 102 b, 102 c over the air interface 116. In one embodiment,the eNode-Bs 140 a, 140 b, 140 c may implement MIMO technology. Thus,the eNode-B 140 a, for example, may use multiple antennas to transmitwireless signals to, and receive wireless signals from, the WTRU 102 a.

Each of the eNode-Bs 140 a, 140 b, 140 c may be associated with aparticular cell (not shown) and may be configured to handle radioresource management decisions, handover decisions, scheduling of usersin the uplink and/or downlink, and the like. As shown in FIG. 1C, theeNode-Bs 140 a, 140 b, 140 c may communicate with one another over an X2interface.

The core network 106 shown in FIG. 1C may include a mobility managementgateway (MME) 142, a serving gateway 144, and a packet data network(PDN) gateway 146. While each of the foregoing elements are depicted aspart of the core network 106, it will be appreciated that any one ofthese elements may be owned and/or operated by an entity other than thecore network operator.

The MME 142 may be connected to each of the eNode-Bs 142 a, 142 b, 142 cin the RAN 104 via an S1 interface and may serve as a control node. Forexample, the MME 142 may be responsible for authenticating users of theWTRUs 102 a, 102 b, 102 c, bearer activation/deactivation, selecting aparticular serving gateway during an initial attach of the WTRUs 102 a,102 b, 102 c, and the like. The MME 142 may also provide a control planefunction for switching between the RAN 104 and other RANs (not shown)that employ other radio technologies, such as GSM or WCDMA.

The serving gateway 144 may be connected to each of the eNode Bs 140 a,140 b, 140 c in the RAN 104 via the S1 interface. The serving gateway144 may generally route and forward user data packets to/from the WTRUs102 a, 102 b, 102 c. The serving gateway 144 may also perform otherfunctions, such as anchoring user planes during inter-eNode B handovers,triggering paging when downlink data is available for the WTRUs 102 a,102 b, 102 c, managing and storing contexts of the WTRUs 102 a, 102 b,102 c, and the like.

The serving gateway 144 may also be connected to the PDN gateway 146,which may provide the WTRUs 102 a, 102 b, 102 c with access topacket-switched networks, such as the Internet 110, to facilitatecommunications between the WTRUs 102 a, 102 b, 102 c and IP-enableddevices.

The core network 106 may facilitate communications with other networks.For example, the core network 106 may provide the WTRUs 102 a, 102 b,102 c with access to circuit-switched networks, such as the PSTN 108, tofacilitate communications between the WTRUs 102 a, 102 b, 102 c andtraditional land-line communications devices. For example, the corenetwork 106 may include, or may communicate with, an IP gateway (e.g.,an IP multimedia subsystem (IMS) server) that serves as an interfacebetween the core network 106 and the PSTN 108. In addition, the corenetwork 106 may provide the WTRUs 102 a, 102 b, 102 c with access to thenetworks 112, which may include other wired or wireless networks thatare owned and/or operated by other service providers.

The reference signals (RSs) may be classified to a wirelesstransmit/receive unit (WTRU)-specific reference (WTRU-RS) and acell-specific reference signaling (CRS). The WTRU-RS may be used onlyfor a specific WTRU so that the RS is transmitted for the resourcesallocated to the WTRU. The CRS may be shared by all WTRUs in the cell sothat the RS is transmitted in a wideband manner. Reference signals maybe further differentiated from a demodulation reference signal (DM-RS)and a channel-state-information reference signal (CSI-RS).

The DM-RS may be used for a specific WTRU and the RS may typically beprecoded to exploit beamforming gain. Since the WTRU-specific DM-RS isnot shared with other WTRUs in the cell, the DM-RS may be transmitted inthe time/frequency resources allocated for the WTRU. The DM-RS may onlybe used for demodulation purposes.

FIG. 2 is an example of a WTRU-specific precoded DM-RS. FIG. 2 includesa precoding entity 200. Stream 0 201 enters the precoding entity 200with a DM-RS 0 202, Stream k-1 203 enters the precoding entity 200 witha DM-RS K-1 204. Stream 0 201 exits the precoding entity 200 with CSI-RS0 205. Stream k-1 203 exits the precoding entity 200 with CSI-RS Nt-1206.

FIG. 2 shows that if a precoded DM-RS is employed, the RS may beprecoded with the same precoding used for data symbols and the samenumber of RS sequences corresponding to the number of layers K istransmitted. Here, K is equal to or smaller than the number of antennaports N_(t).

In FIG. 2, the K streams may be allocated for a WTRU or shared withmultiple WTRUs. If multiple WTRUs share the K streams, the co-scheduledWTRUs may share the same time/frequency resources at the same time. If aprecoded DM-RS is used, a measurement reference signal such as CSI-RSmay be used together for a WTRU to measure channel state information.

The CRS may be defined for all WTRUs in a cell and may be used fordemodulation and measurement purposes. Since the CRS is shared by allWTRUs, a non-precoded RS may typically be employed to keep the cellcoverage uniform. The precoded RS may have different cell coverageaccording to the directions due to the beamforming effect.

FIG. 3 is an example of a non-precoded cell-specific RS. FIG. 3 includesa precoding entity 300. Stream 0 301 enters the precoding entity 300 andexits with a CRS 0 302. Stream k-1 303 enters the precoding entity 300and exits with a CRS Nt-1 304.

FIG. 3 shows an example of a multiple input multiple output (MIMO)transmitter for non-precoded CRS transmission. In some cases, a WTRUtransparent antenna virtualization may be used if the number of physicalantenna elements and logical antenna port is different. The RS sequencesmay be transmitted on all antenna ports irrespective of the number ofstreams.

FIG. 4 is an example of a WTRU-specific DM-RS for a normal CP (port-5).FIG. 4 shows a DM-RS (antenna port-5 400) defined in an LTE system tosupport non-codebook based transmission at an evolved Node B (eNB) andthe antenna port-5 400 only supports one layer transmission. Since theantenna port-5 400 is always transmitted with CRS, the RS overhead intotal may increase significantly.

FIG. 5 is an example of a CRS structure according to the number ofantenna ports. FIG. 5 shows the CRS pattern for 1Tx 501, 2Tx 502, and4Tx 503 antenna ports for a normal cyclic prefix (CP). The CRS patternsfor each antenna ports may be mutually orthogonal in the time/frequencydomain. In FIG. 5, R0 and R1 (for example, 505 and 510, respectively inthe 2Tx 502 antenna port) indicate CRS for antenna port 0 and antennaport 1, respectively. To avoid interference between CRS antenna ports,the data resource elements (REs) located at the RE in which any CRSantenna ports is transmitted may be muted.

A predefined RS sequence (for example, Pseudo-random noise (PN) sequenceand the like) may be transmitted in the RE location for the CRS ports tominimize inter-cell interference, thus improving channel estimationaccuracy from CRS. This PN sequence may be applied at the OFDM symbollevel in a subframe and the sequence may be defined according to thecell-ID, subframe number and the position of the OFDM symbol. Forinstance, the number of CRS antenna ports may be two in an OFDM symbolcontaining CRS per physical resource block (PRB) and the number of PRBsin an LTE system may vary from 6 to 110. In this case, the total numberof CRS for an antenna port in an OFDM symbol containing the RS may be2×N_(RB), which may imply that the sequence length should be 2×N. Here,N_(RB) denotes the number of RBs corresponding to a bandwidth and thesequence may be binary or complex. The sequence r(m) shows the complexsequence.

$\begin{matrix}{{{r(m)} = {{\frac{1}{\sqrt{2}}\left( {1 - {2 \cdot {c\left( {2m} \right)}}} \right)} + {j\frac{1}{\sqrt{2}}\left( {1 - {2 \cdot {c\left( {{2m} + 1} \right)}}} \right)}}},{m = 0},1,\ldots \mspace{14mu},{{2N_{RB}^{DL}} - 1}} & {{Equation}\mspace{14mu} 1}\end{matrix}$

where N_(RB) ^(DL) denotes the number of RB corresponding to the maximumbandwidth in the LTE system, therefore N_(RB) ^(DL) may be 110 asmentioned above. c denotes a PN sequence with length-31 and may bedefined with Gold-sequence. If a DM-RS is configured, the followingequation may be used:

$\begin{matrix}{{{r(m)} = {{\frac{1}{\sqrt{2}}\left( {1 - {2 \cdot {c\left( {2m} \right)}}} \right)} + {j\frac{1}{\sqrt{2}}\left( {1 - {2 \cdot {c\left( {{2m} + 1} \right)}}} \right)}}},{m = 0},1,\ldots \mspace{14mu},{{12N_{RB}^{PDSCH}} - 1}} & {{Equation}\mspace{14mu} 2}\end{matrix}$

where N_(RB) ^(PDSCH) denotes the number of RBs allocated for a specificWTRU. Therefore the sequence length may vary according to the number ofRBs allocated for a WTRU.

To reduce the overall RS overhead, a DM-RS based downlink transmissionmay be introduced in the Release 10 LTE-A system. The CRS may be anon-precoded RS which is common for all WTRUs in a cell, therefore theRS sequences for all antenna ports may need to be transmission always.On the other hand, the DM-RS may be a WTRU-specific precoded RS and thesame precoder used for PDSCH may be used for the DM-RS. In this case,the RS sequences may be transmitted only on the antenna ports used forPDSCH transmission, thus reducing RS overhead as compared with CRS sincethe used number of antenna ports may be smaller than or equal to thenumber of antenna ports used for CRS according to the number of layersfor the PDSCH transmission.

FIG. 6 is an example of a DM-RS pattern supporting up to 8 layers. FIG.6 shows the DM-RS patterns in a PRB for a subframe with a normal CP asan example. FIG. 6 includes two code division multiplexing (CDM) groups,CDM group 1 601 and CDM group 2 602. Also illustrated in FIG. 6 is the 4layer Walsh covering 603 which may be used for CDM multiplexing for eachCDM group. CDM groups may be used for multiplexing up to 4 layers ineach CDM group. Therefore, up to 8 layers may be multiplexed as amaximum in this pattern. For the CDM multiplexing for each CDM group,4×4 Walsh spreading may be used.

Since the DM-RS is only used for demodulation performance, atime/frequency sparse CSI-RS may be introduced for measurement purposes.The CSI-RS may be transmitted with a duty cycle {5, 10, 20, 40, 80} msin the physical downlink shared channel (PDSCH) region. In addition, upto 20 CSI-RS pattern reuse may be available in a subframe as shown inFIG. 7.

FIG. 7 is an example of CSI-RS patterns reuse according to the number ofports. FIG. 7 shows the CSI-RS patters for 2Tx 701, 4Tx, 702, and 8Tx703 antenna ports. In FIG. 7, the same shading implies a set of REs fora particular CSI-RS configuration. The different shaded regionsrepresent Rel-8 CRS 703, a Physical Downlink Control Channel (PDCCH)region 705; Rel 9/10 DM-RS 706, and a Physical Downlink Shared Channel707.

Two types of reporting channels may be used, such as the physical uplinkcontrol channel (PUCCH) and the physical uplink shared channel (PUSCH).The PUCCH reporting channel may provide robust CSI feedback whileallowing limited feedback overhead. The PUSCH reporting channel mayallow a large amount of feedback overhead with less reliability.Therefore, the PUCCH reporting channel may be used for periodic CSIfeedback for coarse link adaptation and the PUSCH reporting may betriggered aperiocally for finer link adaptation.

Table 1 is an example of reporting modes in LTE/LTE-A.

TABLE 1 Reporting modes in LTE/LTE-A Periodic CSI reporting AperiodicCSI Scheduling Mode channels reporting channel Frequency non- PUCCHselective Frequency selective PUCCH PUSCH

CSI feedback may be reported in the format of a rank indicator (RI),precoder matrix index (PMI) and channel quality indicator (CQI). The RIand PMI may be calculated at a WTRU receiver by selecting the rank andthe precoding matrix in the predefined codebook which maximizes WTRUthroughput. The PMI and CQI may be further classified into wideband,subband, and WTRU-selected subband, while RI is only reported in awideband manner.

Table 2 shows further details aperiodic and periodic for CSI feedbackaccording to the transmission mode.

TABLE 2 Rel-8/Rel-9 Details of CSI feedback according to TransmissionModes Transmission Mode Aperiodic Feedback Periodic Feedback 1 Mode 2-0:WTRU selected Mode 1-0: WB CQI 2 sub band CQI: WB CQI + Mode 2-0: WTRU 3CQI over M best Selected sub band CQI: 7 subbands. WB CQI + WTRU reports8 Mode 3-0: high layer(HL) CQI in preferred subband configured subbandCQI: in each BW part, one BW WB CQI + subband CQI. part in eachreporting Notes: opportunity. CQI for first CW only, No Notes: PMI CQIfor first CW only, No PMI 4 Mode 1-2: WB CQI/ Mode 1-1: WB CQI/ 6Multiple PMI: CQI for Single PMI 8 each CW; PMI for each Mode 2-1: WTRUselected 5 subband. subband CQI/Single Mode 2-2: WTRU selected PMI(N_(RB) ^(DL) > 7 only): WB sub band CQI/Multiple CQI/PMI + WTRU PMI:CQI per CW and reports CQI in preferred PMI, both over full BW subbandin each BW part and M best subbands. Mode 3-1: HL configured sub bandCQI/Single PMI: WB CQI + subband CQI, both per CW. Mode 3-1: HLconfigured sub band CQI/Single PMI (see above)

Periodic feedback may be transmitted on the PUCCH, although it may betransmitted on the PUSCH when that channel exists. Periodic reportingmay use a sequence of different types of reports; which may be definedas: Type 1: Subband CQI; Type 2: Wideband CQI/PMI; Type 3: RI; and Type4: Wideband CQI.

FIG. 8 is an example of periodic reporting. A typical reporting sequenceis shown in FIG. 8, where the number in each rectangle corresponds tothe report type above. The type 3 RI may be reported with longest dutycycle which is defined as H×MRI×NP subframes where H, MRI, and NP areconfigured by higher layers. The type 2 802 wideband CQI/PMI may bereported with a longer duty cycle over type 1 803 subband CQI sincesubband CQI is changed more frequently over time due to its short-termchannel characteristic.

Aperiodic feedback may be requested by DCI Format 0 or DCI format 4 whenthe CQI Request bit is set. It may be transmitted on the PUSCH.

In LTE Rel-10, the types of periodic PUCCH feedback may be furtherextended to the following for eight transmit antenna ports: Type 1report supports CQI feedback for the WTRU selected sub-bands; Type 1areport supports subband CQI and second PMI feedback; Type 2, Type 2b,and Type 2c reports support wideband CQI and PMI feedback; Type 2areport supports wideband PMI feedback; Type 3 report supports RIfeedback; Type 4 report supports wideband CQI; Type 5 report supports RIand wideband PMI feedback; and Type 6 report supports RI and PTIfeedback.

In a Type 6 report, the precoding type indicator (PTI) may be used onlyfor 8 transmit antenna ports since the 8-transmit precoder is definedwith a dual codebook.

An active antenna system (AAS) may be a signal processing controlledsmart antenna system. FIG. 9 is a generic block diagram of AAS radioarchitecture. As shown in FIG. 9, an AAS system consists of threecomponents, namely a digital signal processing (DSP) controller 901(also called beam controller), an active transceiver micro-radio unit902, and a passive antenna element. The DSP controller 901 is part ofthe optical CPRI feeder 904. The active transceiver micro-radio unit 902includes a digital upload converter 905 and a duplexer 906. Through theDSP controller units, both the amplitude and phase of the RF signal fedinto each antenna may be dynamically adjusted to change the beamdirection and width.

FIG. 10 is an example concept of vertical sectorization with AAS radioarchitecture. FIG. 10 shows examples of 1 vertical sector 1001, 2vertical sectors 1002, and 3 vertical sectors 1003. The AAS may be usedto form multiple vertical sectors within a cell as shown in FIG. 10,resulting in cell-splitting gain in spatial domain. The vertical sectorsmay be used in either a cell-specific manner or WTRU-specific manner.The vertical sectors using AAS may reduce inter-cell interference whileimproving throughput performance.

FIG. 11 is an example of a WTRU specific elevation beamforming usingAAS. In addition to the vertical sectorization, the AAS 1100 may provideWTRU-specific elevation beamforming gain by using the best elevationbeam for a specific WTRU as shown in FIG. 11. From the WTRU-specificelevation beamforming, the cell coverage or WTRU throughput performancemay be significantly improved.

In LTE, the Random Access (RA) procedure may be used in certainsituations, for example, one or more of the following: 1.) For an RRCConnection Request, such as for initial access or to register; 2.) ForRRC Connection re-establishment, such as following radio link failure;3.) During the Handover to access the target cell; 4.) To obtain uplink(UL) synchronization, such as when UL synchronization is lost anddownlink (DL) data arrives or there is UL data to transmit; 5.) When theWTRU has UL data to transmit and there are no dedicated resources (forexample, no PUCCH resources have been assigned to the WTRU); and 6.) Forpositioning purposes, such as when a timing advance is needed for WTRUpositioning.

There may be two forms of the RA procedure: Contention-based (which mayalso be called common), which may apply to the first five events above,and non-contention based (which may also be called contention free ordedicated), which may apply or only apply to handover, DL data arrival,and positioning.

When using a contention-based RA procedure, the WTRU may initiate theprocess by transmitting a RA preamble randomly chosen from a common poolof preambles which may be communicated to the WTRU by the network, forexample, via broadcasted system information. The WTRU may transmit thepreamble on a PRACH resource (for example, a resource in time andfrequency) that the WTRU chooses from a set of allowed resources, whichmay be communicated to the WTRU by the network, for example, viabroadcasted system information. This set of allowed PRACH resources maybe referred to as the cell's configured set of PRACH resources. The unitof time for the PRACH resource may be a subframe. The subframe the WTRUchooses for the PRACH resource may be the next subframe configured forPRACH in which the WTRU may transmit the PRACH (for example, based ontiming, measurement, and other WTRU constraints). The frequency aspectof the PRACH resource (for example, the resource blocks (RBs)) the WTRUchooses in the selected subframe may be based on parameters communicatedto the WTRU by the network, for example, via broadcasted systeminformation. In certain cases, for example, for frequency divisionduplex (FDD), there may be one frequency resource allowed for PRACH inany subframe. The frequency resource may be defined by a starting(lowest) RB number which may be provided by the network, for example,prach-FrequencyOffset, and may have a fixed bandwidth, such as 6 RBs.

When a contention-based RA procedure is used, it may be possible that atleast two WTRUs select the same resources (preamble and PRACH resource)for random access, and therefore the contention situation may need to beresolved.

When using a non-contention based RA procedure, the WTRU may transmit aRA preamble explicitly signaled to the WTRU by the network, for example,ra-PreambleIndex. The WTRU may transmit the preamble on a PRACH resourcechosen from a specific subset of the cell's configured PRACH resources.The subset (for example, the mask) may be explicitly signaled to theWTRU by the network, for example, ra-PRACH-MaskIndex. In the case thesubset includes only one choice, the WTRU may use the indicatedresource.

In some cases which may be applicable to one or both of the RA proceduretypes, the preamble transmission may span or be repeated over more thanone subframe. In this case, the selected subframe may be the startingsubframe for the transmission.

The terms RACH resources and PRACH resources may be usedinterchangeably.

FIG. 12 is an example of a contention-based RA procedure. The steps ofthe contention-based RA procedure may be as follows.

The WTRU 1201 may transmit 1203 the selected RA preamble on the selectedPRACH resource to an eNB 1202. After transmitting the preamble, the WTRU1201 may read the physical downlink control channel (PDCCH) and look forthe Random Access Radio Network Temporary ID (RA-RNTI) corresponding tothe first subframe on which it transmitted the preamble. If it is notreceived in the response monitoring window, the WTRU 1201 may ramp upthe power, select another resource (possibly after some backoff time),and try again. The RA-RNTI may be determined according to:RA-RNTI=1+t_id+10×f_id, where t_id may be the index of the firstsubframe of the PRACH used for preamble transmission (for example,0≤t_id<10), and f_id may be the index of the PRACH used for preambletransmission within that subframe, in ascending order of frequencydomain (for example, 0≤f_id<6). For the case of one frequency resourceper subframe, for example, for FDD, f_id may be 0.

Random Access Response (RAR) 1204 may consist of a network, for examplethe eNB 1202, transmitting a timing advance command to adjust theterminal transmit timing to the WTRU 1201. The network 1202 may alsoallocate uplink resources for the WTRU 1201 and may transmit a responseon the downlink control channel (PDCCH) using the RA-RNTI to identifywhich WTRU group the allocation is for. Within each group, the RApreamble identifier (RAPID) may be used to narrow down further (forexample, at the medium access control (MAC) level) the WTRU groupspecified by the RA-RNTI to the subset of WTRUs which have used the samepreamble during step 1 of the RA procedure. The RAR 1204 may include oneor more of the index of the RA preamble sequences the network 1202detected and for which the response is valid, the timing correctioncalculated by the RA preamble receiver, a scheduling grant, or atemporary cell identity (TC-RNTI).

For scheduled transmission 1205, the WTRU 1201 may use the allocatedresources indicated by the scheduling grant to transmit 1205 its message(such as RRC Connection Request) to the eNB 1202. If the terminal isconnected to a known cell (for example, in the RRC_CONNECTED state), theterminal may have a C-RNTI (Cell RNTI) which it may include in the ULmessage. Otherwise a core network terminal identifier may be used. TheUL transmission (UL SCH) may be scrambled by the WTRU 1201 using thetemporary TC-RNTI received in the RAR 1204. The scheduled transmission1205 may be referred to as Message 3 (Msg3).

For contention resolution 1206, the network (eNodeB) 1202 may transmit1206 a contention resolution message on the DL based either on theC-RNTI on the PDCCH or a WTRU contention resolution identity on theDL-SCH, for example, the core network terminal identifier transmitted bythe terminal in the scheduled transmission 1205, to the WTRU 1201. Onlythe terminal which observes a match between the identity received in thecontention resolution 1206 and the identity transmitted as part of thescheduled transmission 1205 may declare the RA procedure successful.Contention between WTRUs that chose both the same PRACH time-frequencyresource and the same preamble may be resolved by the contentionresolution 1206.

For contention-based RA, the WTRU may derive the common pool ofpreambles from parameters provided by the network. From theseparameters, the WTRU may derive a full set of preambles, for example, acertain number such as 64 preambles, which may be based on one or moreroot Zadoff-Chu sequences. A parameter which may designate the sequenceor sequences to use may be rootSequenceIndex. The WTRU may receiveadditional parameters indicating a subset of the preambles which may beused by the WTRU and how to divide this subset into two groups, A and B.For example, numberOfRA-Preambles may define the subset of preambles.The first sizeOfRA-PreamblesGroupA may be in Group A (for example,preambles 0 to sizeOfRA-PreamblesGroupA-1), and the remaining preamblesin the subset, if any (for example, sizeOfRA-PreamblesGroupA tonumberOfRA-Preambles-1), may be in Group B. When to use a Group A versusa Group B preamble may be known to the WTRU. The decision may be basedon criteria such as the size of Msg3 and/or pathloss. Preambles in thefull set which are not in Group A or B may be used by the network whenit assigns dedicated preambles.

A PRACH Configuration Index, for example, prach-ConfigIndex, may be usedby the network to tell the WTRU which of a preset list of possibleconfigurations it is choosing for the cell's configured set of PRACHresources. The preset configurations may define, for example for FDD,one or more of the preamble formats, which may define the time for thepreamble cyclic prefix (CP) and the time for the preamble sequence, thesystem frame numbers (SFNs) in which the PRACH is allowed (for example,any, even only, odd only), and the subframes of the allowed SFNs (forexample, a specific 1, 2, 3, 4, 5, or all 10 subframes) in which thePRACH is allowed.

A Power Headroom Report (PHR) may be triggered by a WTRU if any of thefollowing events occur.

A PHR may be triggered if a prohibitPHR-Timer expires or has expired andthe path loss has changed more than dl-PathlossChange dB for at leastone activated Serving Cell which is used as a pathloss reference sincethe last transmission of a PHR when the WTRU has UL resources for newtransmission.

A PHR may be triggered if a periodicPHR-Timer expires.

A PHR may be triggered upon configuration or reconfiguration of thepower headroom reporting functionality by upper layers, which is notused to disable the function.

A PHR may be triggered upon activation of a serving cell (SCell) withconfigured UL.

A PHR may be triggered if: 1) a prohibitPHR-Timer expires or hasexpired, 2) when the WTRU has UL resources for new transmission, and 3)when the following in this transmission time interval (TTI) for any ofthe active SCells with configured UL is true: there are UL resourcesallocated for transmission or there is a PUCCH transmission on thiscell, and the required power backoff due to power management (as allowedby P-MPR_(c)) for this cell has changed more than dl-Pathloss Change dBsince the last transmission of a PHR when the WTRU had UL resourcesallocated for transmission or PUCCH transmission on this cell.

A PHR may be transmitted by a WTRU in a particular TTI (which maycorrespond to a particular subframe) if the WTRU has UL resourcesallocated for new transmission for this TTI (or subframe) and thefollowing applies: the Power Headroom reporting procedure determinesthat at least one PHR has been triggered and not cancelled, and theallocated UL resources may accommodate a PHR MAC control element plusits subheader if extendedPHR is not configured; or the Extended PHR MACcontrol element plus its subheader if extendedPHR is configured, as aresult of logical channel prioritization.

A WTRU may transmit a sounding reference signal (SRS) to the eNB whenconfigured or triggered to do so. The WTRU may transmit SRS in the lastsymbol of a subframe.

SRS transmission by a WTRU may be periodic or aperiodic. Periodic SRStransmission may be configured by the eNB. Aperiodic SRS transmissionsmay be triggered by the eNB, for example, by including a request foraperiodic SRS along with an UL grant.

Cell-specific SRS subframes may be subframes in which the SRS may betransmitted in a given cell. The configuration of cell-specificsubframes may be provided in signaling such as broadcast or dedicatedradio resource control (RRC) signaling.

WTRU-specific SRS subframes may be subframes in which the SRS may betransmitted by a certain WTRU, which may be a subset of thecell-specific SRS subframes. The configuration of WTRU-specificsubframes may be provided to a WTRU in signaling, such as dedicated RRCsignaling. There may be separate WTRU-specific subframes configured fora WTRU for periodic and aperiodic SRS.

When aperiodic SRS is triggered in subframe n, the WTRU may transmit theSRS in the next aperiodic WTRU-specific SRS subframe n+k, where ksatisfies a certain criteria, for example, k>=4.

When one SRS (periodic or aperiodic SRS) and another SRS or channel areboth scheduled to be transmitted in the same subframe, rules and/orconfiguration parameters may govern whether or not the WTRU may transmitthe scheduled SRS.

The aperiodic SRS trigger and the aperiodic SRS request may be usedinterchangeably.

The eNB receiver may estimate a proper downlink vertical beam (forexample, transmit vertical beam) for a specific WTRU based on the uplinkvertical beam (for example, receive vertical beam), thus requiring a SRSfor the receive vertical beam convergence. Since the UL coverage may bedifferent, more than 6 dB between before and after the receive verticalbeam adjustment. Therefore, faster receive vertical convergence mayreduce interference and increase UL throughput. However, current SRSdesign may not allow the faster receive vertical beam convergence, asits transmission has a duty cycle and/or a single subframe transmissionis only possible at a time.

To allow efficient vertical beam adjustment, a WTRU reporting assistedvertical beam selection may be used at the eNB. Since the verticalantenna elements may not be seen by the WTRU, multiple DL referencesignals may be used for a WTRU to select the best vertical beamassociated with a specific reference signal. However, current DLreference signal structure may not allow multiple DL reference signalsor the overhead of multiple DL reference signals may be excessive.

Since the SRS transmission is only available after initial cell access,the PRACH process may not enjoy the benefit of the active antenna system(AAS). In addition, the UL coverage of the PRACH may be worse thanbefore, as the appropriate UL vertical beam for a specific WTRU may notbe estimated at the eNB receiver. Therefore, the PRACH may not haveenough coverage in an AAS as compared with other UL/DL channels.

For the RA procedure, such as the initial RA procedure, to gain initialaccess or transmit the RRC Connection request, it may be desirable toimprove performance by using vertical beamforming. Methods andprocedures may be needed to enable the WTRU to determine a vertical beamfor transmission and for the eNB to know what vertical beam to use forreception.

After receive beam convergence, the power headroom reporting may beupdated immediately since there may be more than a 6 dB differencebetween before and after the receive beam convergence. Current powerheadroom reporting behavior may not support this case. It may be usefulfor the eNB to receive a PHR for a WTRU as soon as possible after thevertical beam it has selected for the WTRU has converged. Methods andprocedures may be needed to accomplish this.

Since a WTRU moves in a cell across multiple vertical sectors/beams, thebest vertical beam for the WTRU may be changed frequently over time. Toprovide appropriate coverage in vertical sectorized cell, WTRU mobilitymay be taken into account even within a cell. Current LTE/LTE-A systemsmay not be flexible to support WTRU mobility across multiple verticalbeams within a cell.

A new UL reference signal may be defined for better receive beamconvergence and the reference signal may be similar to the soundingreference signal (SRS). The UL reference signal for receive beamconvergence may be defined as the Uplink Beam Tracking Reference Signal(u-BTRS).

In a first example, the u-BTRS may be defined in a PUSCH region only,where the PUSCH region implies that the PRBs are not used for the PUCCHin a subframe. In this case, one or more of following may apply.

The u-BTRS may be transmitted in the subframe configured forcell-specific u-BTRS subframe and the last single carrier frequencydivision multiple access (SC-FDMA) symbol, as for SRS. In an example,the cell-specific u-BTRS subframes may be equivalent to thecell-specific SRS subframe. In another example, the cell-specific u-BTRSsubframes may be independently configured and the subframes may bemutually exclusive from the cell-specific SRS subframes. Alternatively,the cell-specific u-BTRS subframes may be independently configured fromcell-specific SRS subframes while subframes may fully or partially beoverlapped between u-BTRS and SRS. In the case of overlapping, at leastone of following may be applied: the u-BTRS transmission has a higherpriority, so that all SRS transmissions in the subframes may be dropped;the SRS transmission has a higher priority, so that all u-BTRStransmissions in the subframes may be dropped; and the subframe may beused either for u-BTRS transmission or for SRS transmission. If bothtransmissions are triggered and/or scheduled in the subframe, the u-BTRSmay have a higher priority and SRS may be dropped, or vice versa.

The u-BTRS may be transmitted in the subframe configured forcell-specific u-BTRS subframe (other than the last SC-FDMA symbol), thusallowing multiplexing of u-BTRS and SRS in the same subframe ifscheduled. In this case, one or more of following may apply: the secondto last SC-FDMA symbol may be used for the u-BTRS subframe; one ofSC-FDMA symbols used for DM-RS may be used for the u-BTRS transmission;the last SC-FDMA symbol in the first slot may be used for the u-BTRStransmission in the subframe; and a SC-FDMA symbol for u-BTRS may beconfigured by a broadcasting channel (for example, SIB-x).

In a cell-specific u-BTRS subframe, even though SRS may be transmittedin all system bandwidth, the u-BTRS may only be transmitted in the PUSCHregion. Therefore, the frequency bandwidth for the u-BTRS in a subframemay be smaller than the SRS. For instance, if a system has 50 PRBs in ULthe SRS may be transmitted in any location of the 50 PRBs according tothe configuration. The u-BTRS may only be transmitted in the centerN_(PUSCH) PRBs for the PUSCH. In this case, at least one of followingmay be applied: N_(PUSCH) and N_(uBTRS) may be used interchangeably,where N_(uBTRS) denotes the PRBs configured for u-BTRS transmissionwhich may be defined irrespective of the PUSCH region; the N_(PUSCH) maybe configured by higher layers, for the indication of N_(PUSCH), thestarting PRB number may be indicated; and N_(PUSCH) may be indicateddynamically in each trigger of u-BTRS.

In second example, multiple SC-FDMA symbols may be used for the u-BTRSin a subframe. If multiple SC-FDMA symbols are used for the u-BTRStransmission, the receive beam convergence time may be reduced. Foru-BTRS transmission in multiple SC-FDMA symbols, one or more offollowing may apply.

The multiple SC-FDMA symbols in a subframe for u-BTRS transmission maybe located within a center N_(PUSCH)/N_(uBTRS) PRBs.

The last N_(uBTRS) SC-FDMA symbols in a subframe may be used for u-BTRStransmission and at least one of following may be used. The N_(uBTRS)may be defined as a predefined integer number. For example, N_(uBTRs)=2or N_(uBTRs)=3 may be used. The N_(uBTRS) may be configured by the eNBvia a broadcasting channel (for example, MIB or SIB-x) or higher layersignaling.

Among the multiple SC-FDMA symbols for u-BTRS transmission, if oneSC-FDMA symbol collides with the SC-FDMA symbol for SRS transmission,the colliding SC-FDMA symbol may not be used for the u-BTRS transmissionin the subframe while the other SC-FDMA symbols may be used.

When multiple SC-FDMA symbols are used for the u-BTRS transmission, theu-BTRS in a SC-FDMA symbol may be repetitively transmitted in the otherSC-FDMA symbols in the same frequency locations.

In a solution for PUSCH transmission, if a WTRU capable for u-BTRStransmission is scheduled for PUSCH transmission in the cell-specificu-BTRS subframe, at least one of following WTRU behaviors may apply. AWTRU may transmit the PUSCH and rate-match around the cell-specificu-BTRS resource in the subframe. A WTRU may transmit the PUSCH if theWTRU is not scheduled to transmit the u-BTRS in that subframe.Otherwise, the WTRU may drop the PUSCH and transmit the u-BTRS in thatsubframe. Alternatively, the WTRU may drop the u-BTRS transmission andtransmit the PUSCH in that subframe.

A DL beam tracking reference signal (d-BTRS) may be defined for thepurpose of vertical beam measurement so that a WTRU may measure multiplevertical beams from the d-BTRS associated with the vertical beams.Assuming that N_(vertical) beams are used in a cell, N_(vertical) d-BTRSmay be configured so that one d-BTRS may correspond to one verticalbeam. In an example, multiple CSI-RS may be used as d-BTRS for multiplevertical beam tracking. In this case, one or more of following mayapply.

Multiple CSI-RS may be configured in a cell-specific manner and eachCSI-RS may be associated with a vertical beam. To configure thecell-specific CSI-RS as d-BTRS, at least one of following may be used.Two or more CSI-RS configurations may be informed to a WTRU via abroadcasting channel (for example, MIB or SIB-x) and the CSI-RSconfigurations may include at least one of: number of antenna ports,duty cycle, pattern, or subframe offset. The number of antenna ports foreach cell-specific CSI-RS configuration may be limited to one or twoantenna ports, which may be independent from the WTRU-specific CSI-RSconfiguration. The cell-specific CSI-RS may be transmitted in a subsetof PRBs. For instance, the cell-specific CSI-RS may be transmitted ineven-numbered PRBs or odd-numbered PRBs. The subset of PRBs for thecell-specific CSI-RS may be informed to a WTRU as a part of CSI-RSconfiguration.

A vertical beam measurement reporting procedure may be defined based onthe multiple cell-specific CSI-RS for better DL vertical beam trackingat the eNB transmitter. For the vertical beam measurement reportingprocedure, WTRU behavior may be defined as at least one of thefollowing. A WTRU may measure two or more cell-specific CSI-RS andmeasure the received signal to noise ratio (SNR) received signal tointerference plus noise ratio (SINR), which may be considered asreference signal received power (RSRP), pathloss, wideband CQI, orsubband CQI. A WTRU may report the measured received SINR for eachcell-specific CSI-RS in a specific UL subframe if scheduled to report ortriggered in the subframe.

An antenna port in a cell-specific CSI-RS may correspond to a specificvertical beam. A single cell-specific CSI-RS may be configured with twoor more antenna ports and each antenna port may be associated with aspecific vertical beam. A WTRU may measure the received SINR for eachantenna port in the cell-specific CSI-RS and report the measured SINRsin a specific UL subframe if scheduled to report or triggered in thesubframe.

In another example, a new measurement RS may be defined as d-BTRS forbetter measurement accuracy as compared with that of CSI-RS.

The new measurement RS (d-BTRS) may be defined with one or more of thefollowing properties. A single antenna port may be defined with 3 or 6subcarrier spacing. An orthogonal frequency division multiplexing (OFDM)symbol in a subframe may be used as a reference signal, resulting in 1subcarrier spacing in the frequency domain. The CSI-RS patterns may bereused with modification.

FIG. 13 is an example of a downlink beam tracking reference signal(d-BTRS) using a four port CSI-RS pattern. For example, a 4-port CSI-RSpattern may be used as a 2-port d-BTRS pattern 1300 as shown in FIG. 13.Therefore, a larger port CSI-RS pattern may be used and modified for asmaller port d-BTRS pattern for a denser RS pattern in the frequencydomain from an antenna port perspective that may include an 8-portCSI-RS pattern used for a 2-port d-BTRS pattern and a 2-port CSI-RSpattern used for a 1-port d-BTRS pattern. For example, by using a 4 portCSI-RS pattern for 2-port d-BTRS as shown in FIG. 13, the frequencyspacing of an antenna port of d-BTRS is 6 subcarriers. However, if2-port CSI-RS pattern is used for a 2-port d-BTRS, the frequency spacingof an antenna port of d-BTRS is 12 subcarriers.

Selection or determination of an RA resource may includeselection/determination of one or more of an RA preamble, an RA preambleformat, and a PRACH resource which may include theselection/determination of the time and/or frequency aspect (forexample, allocation) of the resource. A WTRU may select or otherwisedetermine one or more RA resources based on at least one measurement.

The eNB may provide and the WTRU may receive one or more measurementconfigurations where each measurement configuration may correspond to asignal the eNB may transmit with one or more certain characteristics.For example, the signal may include a certain vertical (or DL vertical)beam.

In the descriptions herein, vertical and DL vertical beams are examplecharacteristics. Any other characteristics may be used and still beconsistent with this description.

The configuration may be signaled by the eNB to the WTRU via higherlayer signaling such as broadcast or dedicated RRC signaling.

A measurement configuration may include the parameters needed by theWTRU to make the measurements, such as: the time schedule of themeasurement (for example, which frames and subframes), frequencylocation, measurement identifier, the type of measurement, or otherparameters specific to the type of measurement.

Separate from, or as part of, a measurement configuration, the eNB mayindicate an association of a measurement (or measurement configuration),which may correspond to a certain transmission characteristic such as avertical beam, with a certain set of RA resources or RA parameters.

The RA resources or RA parameters may include or may enable the WTRU todetermine: a set of one or more RA preambles, the preamble format forthe RA preambles, or a set of one or more PRACH resources which mayinclude an allocation in frequency and/or time. This indication may besignaled by the eNB to the WTRU via higher layer signaling such asbroadcast or dedicated RRC signaling.

The indication may include any parameters necessary to convey thecertain set of RA parameters. For example, the parameters may include:one or more indices into one or more tables with predefinedconfigurations which may, for example, define the frames and/orsubframes to use; one or more masks to use with another configuration(or configurations) that define a larger set of resources; specificpreamble number (or index); starting preamble number (or index); numberof preambles; frequency offset for first RB; or Number of RBs.

Indication of association and/or random access or other relatedparameters may be provided for individual measurements (or measurementconfigurations) and/or groups of measurements (or measurementconfigurations).

A set of RA resources may currently be provided in a cell forcontention-based RA. Since all WTRUs may use these resources and the eNBmay not have certain information about these WTRUs, the eNB may not beable to treat reception of RA preambles from different WTRUs differentlyeven if it may be desirable to do so.

One way to enable the eNB to recognize a certain purpose orcharacteristic of the WTRU transmitting a preamble may be to designatecertain RA resources to be used by WTRUs for a certain purpose or with acertain characteristic. For example, the certain characteristic may be apreferred or selected beam direction. The eNB may designate certain RAresources, for example, certain RA preambles and/or PRACH resources, tobe used by WTRUs that prefer or select a certain one or more verticalbeam directions in the UL and/or DL. For reception of these preamblesand/or resources, the eNB may use a specific UL vertical beam that mayachieve better reception performance.

As another example, the certain characteristic may be that the WTRU hasdetermined that a measurement it makes warrants use of a certain set ofRA resources (for example, certain RA preambles and/or PRACH resources).For example, if a measurement a WTRU makes meets a certain criteria, theWTRU may choose and/or use an RA resource (for example, RA preambleand/or PRACH resource) in a set of RA resources (for example, RApreambles and/or PRACH resources) associated with that measurement orthe configuration of the measurement.

A set of RA resources may be allocated by the eNB and/or used by a WTRUfor RA transmission when the WTRU has a certain characteristic orpurpose.

A set of RA resources associated with a certain characteristic orpurpose may include a set of RA preambles and/or PRACH resources whichmay have one or more of the following aspects different from the RApreambles and PRACH resources designated in the cell forcontention-based RA: preambles, time aspect (or allocation) of the PRACHresources, or frequency aspect (or allocation) of the PRACH resources.

When selecting RA resources, a WTRU with a certain purpose orcharacteristic may (or may only) choose an RA resource (for example,including preamble and PRACH resource in time and frequency) which is inthe set of RA resources allowed or designated for use for the certainpurpose or characteristic.

For the set of RA preambles which may be used for a certain purpose orcharacteristic, one or more of the following may apply.

The set of RA preambles may be a designated subset of the cell'sexisting full set of preambles. The set may be within the subset of thefull set that is not part of Group A or Group B.

The set of RA preambles may be a separate set of preambles from thecell's existing full set of preambles. The set may have its own rootZadoff-Chu sequence or sequences. Given multiple purposes orcharacteristics, for example, vertical beams or measurementconfigurations, there may be a set (or multiple sets) of preamblesseparate from the cell's existing full set of preambles and each purposeor characteristic may be associated with a subset of that set (or one ofthose sets).

One set of preambles may be designated for a group of purposes orcharacteristics, for example, a group of vertical beams or measurements(or measurement configurations). Given N purposes or characteristics inthe group, the set of preambles may be divided, for example, equally,among the group with understanding between the WTRU and eNB, forexample, based on explicit or implicit configuration, as to whichpreambles correspond to which member of the group. When measurements arethe characteristic, the understanding may, for example, be based on themeasurement identity or the order of the measurement configurations,such that if a WTRU chooses a RA preamble based on a particularmeasurement meeting a criteria, it knows from which set of preambles tochoose.

The set of RA preambles may be the preambles in the existing Group Aand/or B. In this case, preamble may not be used by the eNB tounderstand the purpose or characteristic.

The RA preamble format for the set of preambles may be different. Forexample, one or more certain CP lengths, for example, longer thancurrently used for a given preamble format, may be used for a certainpurpose or characteristic.

For the set of PRACH resources which may be used for a certain purposeor characteristic, one or more of the following may apply.

The frequency allocation of the PRACH resources may be separate ordifferent from the frequency allocation for the cell's existing set ofPRACH resources. Each purpose or characteristic may have its ownfrequency resource where the starting RB may be designated. One newfrequency resource may be designated for a group of purposes orcharacteristics, for example, all vertical beams or all of a certaintype of measurement.

The time allocation of the PRACH resources may be separate or differentfrom the time allocation for the cell's existing set of PRACH resources.Each purpose or characteristic may have its own time allocation. One newtime allocation may be designated for a group of purposes orcharacteristics, for example, all vertical beams. The time allocationfor one or a group of purposes or characteristics may be accomplished bydesignation of a specific PRACH configuration index and/or PRACH Maskindex where the configurations and masks corresponding to these indicesmay be those which currently exist, for example, for allpurposes/characteristics and/or new configurations and masks may beused. For the case of a group of purposes or characteristics, if onePRACH configuration index is provided, the WTRU may understand how todivide the time resources among the members of the group based on, forexample, certain configuration information it may receive such as beamor measurement identities or the order of beams or measurementsconfigured or in a configuration. To minimize impact to a system whenthere may be a number of purposes or characteristics, the timeallocation for a purpose or characteristic may be sparser than currentlyallowed, for example, sparser than every other frame.

A WTRU may select or otherwise determine a RA resource to use for RAtransmission, or a set of RA resources which may be used for RAtransmission, based on at least one of the following: one or moremeasurements; WTRU determination that one or more measurements meet acertain criteria; the result of a comparison made by the WTRU of atleast one measurement against one or more quality criteria orthresholds; the result of a comparison of two or more measurements; WTRUselection of a measurement based on certain criteria being met and/orthe results of comparison with one or more other measurements; and theassociation of a measurement with one or a set of RA resources.

The result of a comparison made by the WTRU of at least one measurementagainst one or more quality criteria or thresholds. For example, theselection or determination may be based on the WTRU determining that ameasurement is better (or worse) than a threshold. Better may meangreater in value and worse may mean lower in value. For example, theWTRU may make an RSRP measurement using the CRS of the cell and if thatmeasurement is above a threshold, the WTRU may determine that the cell'sexisting set of RA resources (for example, RA resources which may not beassociated with a certain purpose or characteristic such as verticalbeamforming) may be used.

The result of a comparison of two or more measurements. For example, theselection or determination may be based on the WTRU determining that ameasurement is better (or worse) than at least one other measurement.For example, the selection or determination may be based on the WTRUdetermining a measurement is the best of a set of measurements. Bettermay mean greater in value, for example by at least a certain threshold.Worse may mean lower in value, for example by at least a certainthreshold. Other quality criteria instead of or, in addition to, valuemay be used to determine whether one measurement is better (or worse)than another measurement. At least one of the measurements may need tomeet certain other criteria, for example, quality criteria, to beincluded in the comparison. For example, a measurement value may need toexceed a threshold in order to be included in the comparison.

WTRU selection of a measurement based on certain criteria being metand/or the results of comparison with one or more other measurements.For example, WTRU selection of a certain measurement as the bestmeasurement which may correspond to the WTRU selection of the bestvertical beam.

The association of a measurement with one or a set of RA resources. Theassociation of measurements with RA resources may be configured by theeNB, for example, as described elsewhere herein.

The one or more measurements may be configured by the eNB, which maymean signaled to the WTRU via higher layer signaling, such as broadcastor dedicated RRC signaling. Such configuration may be as describedelsewhere herein.

Any thresholds a WTRU may use may be signaled to the WTRU by the eNB,for example by broadcast or dedicated signaling.

The one or more measurements may be made by the WTRU. The comparisonsmay be performed by the WTRU. The determination as to whether criteriaare met may be performed by the WTRU.

When the selection/determination is of a set of RA resources which maybe used for transmission, the WTRU may choose the specific RA resourcebased on rules similar to the existing rules or new rules may bedefined.

For example, if there are multiple preambles to choose from, the WTRUmay choose one randomly. If there are different preambles to choose fromwith certain criteria to be met such as for the current Group A and Bpreambles, the WTRU may choose a preamble taking into account thosecriteria. If there are multiple frequency resources to choose from, theWTRU may choose one randomly. For the time aspect, the WTRU may choosethe first available subframe in the set of RA resources in which it ispermitted to transmit the preamble and may meet its time constraints.

In one example, a WTRU may make at least two measurements. The WTRU maycompare the measurements and determine which measurement is best. TheWTRU may select or determine the set of RA resources associated with thedetermined best measurement. The WTRU may then select or determine an RAresource from within the determined set of RA resources and the WTRU mayuse that resource for RA transmission.

In another example, the WTRU may first determine if the measurementsmeet a certain quality criteria such as whether they exceed a threshold.The WTRU may or may only include measurements in the comparison if theymeet the certain criteria. If only one measurement may meet the qualitycriteria, then that measurement may be considered the best measurementby the WTRU.

In another example, the WTRU may first determine whether a certaincriteria is met, such as whether the RSRP of the cell exceeds athreshold. If that criteria is met, then the WTRU may use the legacy RAresources for RA transmission. If the criteria is not met, then the WTRUmay determine which RA resources to use based on the results ofcomparisons of measurements associated with RA resources.

The measurement may be a reference signal (RS), where the referencesignal may be: a cell-specific RS (CRS), a channel-state information(CSI) RS, a vertical beam (VB) RS, or any other RS or known signal whichmay be received by the WTRU or transmitted by an eNB.

If measurements of different types are to be compared by the WTRU, theeNB may provide parameters to the WTRU to enable the WTRU to adjust oneor more of the measurements prior to comparison, for example, to bettercorrelate the measurements.

The WTRU may make and compare measurements that are for all purposes andcharacteristics (for example, existing or legacy measurements) withmeasurements which may be associated with certain purposes orcharacteristics.

The WTRU may do this without additional configuration from the eNBregarding the existing/legacy measurements. The WTRU may understand thatthese are associated with existing/legacy RA resources.

The WTRU may be provided with multiple, for example, one or more sets ofRA resources that the WTRU may understand are to be used for certainpurposes or characteristics. For example, the WTRU may understand thateach RA resource set corresponds to a different vertical beam (where theWTRU may or may not know what each beam direction is), measurement, ormeasurement configuration. One of these sets may be the RA resource setwhich may be used for existing/legacy purposes.

The WTRU may, for example, if it has no knowledge of which set ofresources may be better, do one or more of the following: choose, forexample, randomly, one set from the multiple RA resource sets; select aRA resource within the set according to the selection rules (forexample, random selection of preamble in the set, first availablesubframe in the set that may meet the physical timing constraints, andthe like); perform the RA procedure (which may include transmitting theselected preamble at a certain power); wait for a RAR; and if no replyis received, the WTRU may ramp the power up and try again, which mayinclude repeating the RA resource selection from the currently selectedRA resource set and ramping power until it receives an RAR or reachesthe maximum allowed power ramping or ramping attempts.

If the WTRU reaches the maximum allowed power ramping or rampingattempts, the WTRU may then select, for example, randomly, another setof RA resources if one exists and then try again.

The order in which the WTRU chooses a set of RA resources may beaccording to one or more of the following.

The WTRU may select the RA set to be used for existing/legacy purposesfirst. The WTRU may determine to select the RA set to be used forexisting/legacy purposes first if it determines a measurement, such as aRSRP measurement, exceeds a certain threshold.

The WTRU may select an RA resource set randomly from the multiple setsprovided.

Each time a WTRU selects an RA set, it may select the set randomly fromthe multiple sets provided or from the subset of the multiple sets thatdoes not include a set already tried.

The WTRU may select an RA resource set according to an order configuredby the eNB where such configuration may be signaled to the WTRU by theeNB via signaling, such as broadcast or dedicated RRC signaling.

The WTRU may use measurements to determine which RA resource set to tryfirst or the order in which to try the RA resource sets. Whenmeasurements are used, the WTRU may select the RA resource set thatcorresponds to the measurement or measurement configuration that meets acertain criteria.

An eNB may use measurements of SRS transmissions from a WTRU todetermine a preferred beam direction for UL reception from and/or DLtransmission to the WTRU.

The eNB may use aperiodic SRS to cause the WTRU to transmit SRS atspecific time.

To enable the eNB to get a number of SRS transmissions, for example toenable convergence of the beam direction, the eNB may trigger aperiodicSRS a number of times, where such triggers may be closely spaced intime. For example, the eNB may trigger N aperiodic SRS for a WTRU suchthat the WTRU is scheduled to transmit and/or transmits SRS in Nconsecutive WTRU-specific SRS subframes. Consecutive WTRU-specific SRSsubframes may not be consecutive subframes, since only certain subframesmay be WTRU-specific SRS subframes.

To enable the eNB to get a number of SRS transmissions, for example toenable convergence of the beam direction, the eNB may trigger amulti-shot aperiodic SRS which may yield the result that the WTRU isscheduled to transmit and/or transmits SRS in N consecutiveWTRU-specific SRS subframes. The first subframe in which the WTRUtransmits SRS may be the first WTRU-specific subframe that is at least ksubframes after the subframe in which the trigger is received, where kmay be 4. N may be a known value, a configured value, or a valueprovided with the trigger.

It may be useful for the eNB to receive a PHR after the vertical beamhas converged.

To accomplish this, the WTRU, for example, may trigger a PHR accordingto at least one of the following: upon receipt of an aperiodic SRSrequest which may also include a PHR request; a certain time T, or anumber of TTIs or subframes S, after receiving an aperiodic SRS request;a certain time T, or a number of TTIs or subframes S, after transmittingan aperiodic SRS; a certain time T, or a number of TTIs or subframes S,after transmitting the last of the N SRS transmissions triggered by amulti-shot aperiodic SRS request; and a certain time T, or a number ofTTIs or subframes S, after receiving a group of closely spaced aperiodicSRS requests. For example, if a WTRU receives an aperiodic SRS requestin the span of less than B ms, the WTRU may trigger PHR C ms or TTIs orsubframes after the last trigger or after the last SRS it transmits inthat time span.

The time T or number of subframes S may be at least one of: a knownvalue, for example, by a rule; configured such as by higher layersignaling; included with the aperiodic SRS request; selected, such asfrom a set of known or configured values, by an indication which may beincluded in the aperiodic SRS request; or greater than or equal to 0.

PHR may or may only be triggered based on receipt of an aperiodic SRSrequest if the aperiodic SRS request includes a PHR request.

If it is not possible for the WTRU to transmit the PHR, for example ifthere are no UL resources allocated for new transmission in which thePHR may fit, when the PHR is triggered, the WTRU may transmit the PHR atthe soonest later time when transmitting a PHR is possible.

Once the criteria for triggering an aperiodic SRS related PHR has beenmet, the WTRU may continue to trigger this PHR until the PHR istransmitted or able to be transmitted.

For the DL, an eNB with 3D-MIMO/3D-beamforming capabilities in generalmay require DL CSI to precisely shape the beam for a specific WTRU,which may be called WTRU-specific beamforming. The DL CSI may beobtained with the above proposed CSI feedback includingPMI/CQI/RI/RSRP/PTI/CPI and the like. The eNodeB may also predefine aset of vertical beams (within a single horizontal cell). As mentionedabove, each vertical beam may be associated with a specific CSI-RSconfiguration. To support N_(v) vertical beams, N_(v) CSI-RSconfigurations may be used for a WTRU to measure the multiple verticalbeams. A WTRU may measure and report channel state information (CSI)based on a single or multiple CSI-RS configurations. The CSI-RS andd-BTRS may be interchangeably used herein. Therefore multiple CSI-RSconfigurations may be equivalent to the multiple d-BTRS. In addition,the d-BTRS may be whole or a subset of the antenna ports in a CSI-RSconfiguration, which may include the solution that a single CSI-RSconfiguration with N-ports may be divided into multiple subsets and eachsubset corresponding to a d-BTRS.

As a WTRU moves from one location to another location (in the verticaland/or horizontal domain), the desired WTRU-specific 3-D beam (verticaland/or horizontal) may have changed in either the vertical domain, thehorizontal domain, or both. Thus the desired WTRU-specific beam may needto be updated either through a WTRU or an eNodeB triggered event. Tosupport WTRU-specific 3D beamforming, one or more of following mayapply.

For any given TTI, a WTRU may measure all the CSI-RS configurations andreport the multiple CSI information (representing the vertical beamquality). This may introduce excessive feedback overhead. Alternatively,a WTRU autonomous behavior may be needed to report the best or preferredvertical beam when the desired vertical beam of the WTRU changes due tomovement.

The procedure may be defined as follows. A WTRU k may calculate itswideband SINR γ_(k)(H_(k), V_(k)) as a function of channel stateinformation and applied vertical beamforming (reflected in a currentactive CSI-RS port). The WTRU may measure all the configured CSI-RSports and calculate the SINRs. Once the SINR of the current activeCSI-RS port (corresponding to current vertical beam) drops more than adefined threshold compared to other configured CSI-RS ports(representing different vertical beams), for example:

γ_(k) ¹(H _(k) ¹ V _(k) ¹)−γ_(k) ⁰(H _(k) ⁰ , V _(k) ⁰)>Γ_(th)

γ_(k) ⁰: SINR at an original location measured on current active CSI-RSport

γ_(k) ¹: SINR at a new location measured on any other configured CSI-RSport

Γ_(th): SINR threshold for beam reselection

the WTRU may then report back the strongest CSI-RS port associated withthe measured strongest SINR along with an indication of beam update. TheeNB may accordingly update the active vertical beam for the WTRU forfuture transmission. The active vertical beam update may includereconfiguration of the active CSI-RS port. The SINR metric may bereplaced with RSRP or RSRQ with the same procedure. Either subband orwideband CSI may be used.

A WTRU may be triggered to report the preferred CSI-RS configurationamong the multiple CSI-RS configurations by one or more of following.

The preferred CSI-RS configuration may be defined as at least one of:the CSI-RS configuration having the highest wideband CQI (or RSRP) valueamong the set of CSI-RS configurations, or the CSI-RS configuration aWTRU preferred to report for CSIs including CQI/PMI and/or RI.

An eNB may trigger to report the preferred CSI-RS configuration amongthe multiple CSI-RS configurations from a DCI. A triggering bit may beincluded in the DCI and if the triggering bit indicates ‘0’, the WTRUmay not report the preferred CSI-RS configuration and if the triggeringbit indicates ‘1’, the WTRU may report the preferred CSI-RSconfiguration in the corresponding UL subframe. The corresponding ULsubframe may be n+4, where n is the subframe index where the WTRUreceived the triggering.

A WTRU may report the preferred CSI-RS configuration if at least one offollowing conditions is satisfied. The previous preferred CSI-RSconfiguration has a lower wideband CQI (or RSRP) than any of the otherCSI-RS configurations in a subframe k and the gap between the bestCSI-RS configuration and the previous preferred CSI-RS configuration islarger than a predefined threshold value. The CSI-RS configurationhaving the highest wideband CQI (or RSRP) is changed and the gap islarger than a predefined threshold.

A WTRU may be configured to report the preferred CSI-RS configurationperiodically. For instance, in every N_(cycle) [ms], a WTRU may report apreferred CSI-RS configuration. In this case, one or more of followingmay apply:

The preferred CSI-RS configuration may be reported as V_(index) and theV_(index) may be reported by any one of: separately from PMI/RI/CQIand/or PTI, or via the PUCCH using PUCCH format 2/2a/2b.

The preferred CSI-RS configuration (for example, V_(index)) may bereported via the PUSCH in a piggybacked manner. In this case, thelocation of the Vindex may be the same as the RI.

A WTRU may be configured with multiple CSI-RS configurations while theCSI reporting (for example, CQI/PMI/RI and/or PTI) may be based on anassociated CSI-RS configuration, where the associated CSI-RSconfiguration may be informed by the eNB. In this case, one or more offollowing may apply:

The associated CSI-RS configuration may be informed via higher layersignaling. The associated CSI-RS configuration may be indicated in a DCIfor UL grant if aperiodic CSI reporting is used. A WTRU may report thepreferred CSI-RS configuration via higher layer signaling. Theassociated CSI-RS configuration may be informed implicitly by confirmingthat the eNB received the preferred CSI-RS configuration reporting.Thus, right after the confirmation, the WTRU may measure CSI based onthe reported preferred CSI-RS configuration. The multiple CSI-RSconfigurations may be measured only for reporting the preferred CSI-RSconfiguration.

The multiple CSI-RS configurations are cell-specific, which is differentfrom WTRU-specific CSI-RS configuration. A WTRU may measurecell-specific CSI-RS configurations (for example, d-BTRS) for reportingpreferred CSI-RS configuration, while the WTRU may measure WTRU-specificCSI-RS configurations for CSI reporting for one or more transmissionpoints. In this case, one or more of following may apply:

A WTRU may report based on cell-specific CSI-RS configurations if one ormore of following conditions are met. The previous preferredcell-specific CSI-RS configuration has a lower wideband CQI (or RSRP)than any of other cell-specific CSI-RS configurations in a subframe kand the gap between the best cell-specific CSI-RS configuration and theprevious preferred cell-specific CSI-RS configuration is larger than apredefined threshold value. The cell-specific CSI-RS configuration thehaving highest wideband CQI (or RSRP) is changed and the gap is largerthan a predefined threshold.

A WTRU may report based on WTRU-specific CSI-RS configurations if theeNB configures periodic CSI reporting or triggers aperiodic CSIreporting.

In the case of line of sight (LoS), the above beam reselection may becomplemented with a direction of arrival-triggered beam update. The eNBmay decide and change the beam for the WTRU based on qualified triggerevents. This case is suitable for the LoS case only and low mobility.

The eNB may detect the direction of arrival (DoA) for both azimuth andelevation from each WTRU. Once the measured DoA change from a WTRUreaches a threshold, the eNB may adjust the WTRU to a newdirection-based pre-defined vertical beam.

FIG. 14 is an example method for receiving a reception vertical beam. Awireless transmit/receive unit (WTRU) 1401 may receive 1403 a broadcastmessage from an evolved Node B (eNB) 1402 that includes informationassociated with a plurality of vertical beams, wherein the informationincludes at least one set of Physical Random Access Channel (PRACH)resources associated with each of the plurality of vertical beams. TheWTRU 1401 may measure 1404 reference signals transmitted on each of theplurality of vertical beams to select a reception vertical beam. TheWTRU 1401 may transmit 1405 a PRACH preamble in a set of resourcesassociated with the selected reception vertical beam. The WTRU 1401 mayreceive 1406 communications from the eNB 1402 using the selectedreception vertical beam.

Although features and elements are described above in particularcombinations, one of ordinary skill in the art will appreciate that eachfeature or element may be used alone or in any combination with theother features and elements. In addition, the methods described hereinmay be implemented in a computer program, software, or firmwareincorporated in a non-transitory computer-readable medium for executionby a computer or processor. Examples of non-transitory computer-readablemedia include electronic signals (transmitted over wired or wirelessconnections) and computer-readable storage media. Examples ofcomputer-readable storage media include, but are not limited to, a readonly memory (ROM), a random access memory (RAM), a register, cachememory, semiconductor memory devices, magnetic media such as internalhard disks and removable disks, magneto-optical media, and optical mediasuch as CD-ROM disks, and digital versatile disks (DVDs). A processor inassociation with software may be used to implement a radio frequencytransceiver for use in a WTRU, UE, terminal, base station, RNC, or anyhost computer.

What is claimed is:
 1. A method for use in a wireless transmit/receiveunit (WTRU) for determining resources, the method comprising: measuring,by the WTRU, a plurality of beam reference signals transmitted from abase station; selecting, by the WTRU, a beam reference signal from amongthe plurality of measured beam references signals; receiving, by theWTRU, a configuration message, wherein the configuration message is atleast one of a broadcast message or a radio resource control (RRC)message, from the base station that includes correspondence informationregarding the plurality of beam reference signals, wherein thecorrespondence information designates at least one set of PhysicalRandom Access Channel (PRACH) resources for each of the plurality ofbeam reference signals; determining, by the WTRU, a set of PRACHresources designated for the selected beam reference signal based on thereceived correspondence information; and transmitting, by the WTRU, aPRACH signal using at least one PRACH resource of the determined set ofPRACH resources.
 2. The method of claim 1, wherein the correspondenceinformation regarding the plurality of beam reference signals includes aplurality of measurement configurations.
 3. The method of claim 1,wherein the determined set of PRACH resources includes at least onePRACH preamble and wherein the PRACH signal is a PRACH preamble in thedetermined set of PRACH resources.
 4. The method of claim 1, wherein theWTRU selects a beam reference signal based on a determination that ameasured beam reference signal power is better than a threshold on atleast one beam reference signal.
 5. The method of claim 1, wherein theat least one set of PRACH resources is portioned based on the number ofthe plurality of beam reference signals.
 6. The method of claim 1,wherein the beam reference signals are Channel StateInformation-Reference Signals (CSI-RSs).
 7. The method of claim 1,wherein the determined set of PRACH resources includes at least one setof time resources and wherein the PRACH signal is transmitted in one ofthe time resources of the set of time resources.
 8. The method of claim1, wherein the beam is a 3-D beam.
 9. The method of claim 1, furthercomprising: determining, by the WTRU, the PRACH signal based on thereceived correspondence information.
 10. A wireless transmit/receiveunit (WTRU) for determining resources, the WTRU comprising: a processor,operatively coupled to a transceiver, the processor and the transceiverconfigured to measure a plurality of beam reference signals transmittedfrom a base station; the processor configured to select a beam referencesignal from among the plurality of measured beam references signals; thetransceiver configured to receive a configuration message, wherein theconfiguration message is at least one of a broadcast message or a radioresource control (RRC) message, from the base station that includescorrespondence information regarding the plurality of beam referencesignals, wherein the correspondence information designates at least oneset of Physical Random Access Channel (PRACH) resources for each of theplurality of beam reference signals; the processor configured todetermine a set of PRACH resources designated for the selected beamreference signal based on the received correspondence information; andthe processor and the transceiver configured to transmit a PRACH signalusing at least one PRACH resource of the determined set of PRACHresources.
 11. The WTRU of claim 10, wherein the correspondenceinformation regarding the plurality of beam reference signals includes aplurality of measurement configurations.
 12. The WTRU of claim 10,wherein the determined set of PRACH resources includes at least onePRACH preamble and wherein the PRACH signal is a PRACH preamble in thedetermined set of PRACH resources.
 13. The WTRU of claim 10, wherein theprocessor selects a beam reference signal based on a determination thata measured beam reference signal power is better than a threshold on atleast one beam reference signal.
 14. The WTRU of claim 10, wherein theat least one set of PRACH resources is portioned based on the number ofthe plurality of beam reference signals.
 15. The WTRU of claim 10,wherein the beam reference signals are Channel StateInformation-Reference Signals (CSI-RSs).
 16. The WTRU of claim 10,wherein the determined set of PRACH resources includes at least one setof time resources and wherein the PRACH signal is transmitted in one ofthe time resources of the set of time resources.
 17. The WTRU of claim10, wherein the beam is a 3-D beam.
 18. The WTRU of claim 10, furthercomprising: the processor further configured to determine the PRACHsignal based on the received correspondence information.
 19. A methodfor use in a wireless transmit/receive unit (WTRU) for determiningresources, the method comprising: measuring, by the WTRU, a plurality ofbeam reference signals transmitted from a base station; selecting, bythe WTRU, a beam reference signal from among the plurality of measuredbeam references signals; receiving, by the WTRU, a configurationmessage, wherein the configuration message is at least one of abroadcast message or a radio resource control (RRC) message, from thebase station that includes correspondence information regarding theplurality of beam reference signals, wherein the correspondenceinformation provides at least one set of Physical Random Access Channel(PRACH) preambles, wherein the set of PRACH preambles includes one ormore PRACH preambles, for each of the plurality of beam referencesignals; determining, by the WTRU, a set of PRACH preambles designatedfor the selected beam reference signal based on the receivedcorrespondence information; and transmitting, by the WTRU, a PRACHpreamble of the determined set of PRACH preambles.
 20. The method ofclaim 19, wherein the correspondence information regarding the pluralityof beam reference signals includes a plurality of measurementconfigurations.